Electric soldering iron



Nov. 2, 1943. J. E. SMITH 2,333,207

ELECTRIC SOLDERING IRON Original Filed April 29, 1958 INVENTOR.

BY I

ATTORNEY.

Patented Nov. 2, 1943 UNITED STATES 12,333,207

. ELECTRIC SOLDERING IRON John ErneSt Smith, Plainfiel'd, N. J.

firiginaldapplication April 29, 1938, SerialNo.

Divided and this ,a-pDlicationiMamh .5 Claims.

This invention relates to electrically heated soldering irons and-moreparticularly 'to means for maintainingan even tip temperature.

Thisapplication-is a division of my co-pending application, Serial No.'205,047,filed April 29, 1938, Patent No. 2,192,655.

It is one object of my invention to provide an electrically heatedsoldering iron "in which the temperature at the working tip will bemaintained substantially constant both during "the time of use'andduring the-time of non-use, the advantage beingthat once the solderingiron is connected to the source of electricity and brought up to workingtemperature, it will be ready for use instantaneously without anyattention on the part of the operator.

It is another object of my invention to provide a construction andarrangement of the parts of a soldering iron so that they will bereadily assembled and manufactured into a structure sturdy andserviceable and in which repairs, replacements and adjustments may bevery easily made.

It is a further object of my invention to provide a soldering iron andan electrical heater therefor with means whereby the working temperatureof the soldering tip may be varied to suit the particular conditions ofuse.

Other and further objects of my invention will be apparent from thisspecification taken in conjunction with the accompanying drawing whereinthe single figure is an elevational view with parts broken away andshown in transverse section of a soldering iron embodying the featuresof my invention.

A heater I, which may be constructed as more particularly described inmy co-pending application referred to above, comprises a cylindricalbody of cast aluminum which encloses an electrical heating element ofcoiled resistance wire that is embedded in ceramic material. In theconstruction illustrated, a strand of the heating element extendsbetween the terminal pins 2 and 3 respectively on opposite ends of theheater l and a second strand of the heating element extends betweenterminal pins 4 and 5 likewise on opposite ends of the heater. Theterminal pins 2 to 5 inclusive are rigidly supported in and by the metalbody of the heater l. The heater body is provided with reduced portions6 and I on opposite ends thereof which are screw-threaded. A handle 8 ofinsulating material screws upon the threaded projection 6 and asoldering tip 9 screws upon the threaded projection l. A pair of wiresl0 extend longitudinally through the handle 8 and arerespectivelymounted.upon the terminalpins '2 and 4 which are housedwithin cavityil I of the handle.

The soldering tip 'is'hollow except for the Working tip portionlZ.Mounted on .terminal pins 3 and'5 area pair of strips l3, each of whichcarries one of a pair of contact members .M and one or the other ofwhich is'formed from thermometalor'bimetallic strip stock. Thus thecircuit for the heating element may be traced from one of the wires l0that are connected to .theosource of power through the terminal pin 2 tothe heatingelement, the terminalpin 3,.thecontact members M, theterminalpinfii, .the heating element connected thereto and the terminalpin 6 and thence through "the other 'wire' H1. Also mountedon-the'terminal pin "3 is'another strip of metal 15 which carries anadjusting screw It in position to engage one of the contact strips l3.

As will be seen from the drawing, the arms [3 of the thermo-switchextend through the hollow tip 9 and adjacent to the working tip 12. Inany event, the chamber in which the thermoswitch is located is directlyresponsive to variations in tip temperature. The working temperature ofthe tip can be adjusted to whatever are the conditions under which thesoldering iron is being used, and if variations in temperature are duemerely to the ambient conditions, as when the soldering iron is at rest,or whether the reduction in tip temperature is caused by its applicationto the work which thus reduces the temperature on the interior of thehollow tip, the result will be the immediate energization of the heatingelement to restore the tip temperature to its desired level. Thedescribed arrangement will be effective to maintain a substantiallyconstant temperature at the tip.

On the other hand, if the heater and soldering iron are so proportionedthat thermostatic regulation is not necessary to maintain the tiptemperature constant within the practical limits needed, then thethermostatic switch can be adjusted to function as a protective devicefor the heating element to keep the same from burning out under improperconditions of use or non-use.

It may be pointed out that the heater body I is of aluminum or othermetal of high thermal conductivity while the soldering tip is desirablyof copper. The handle is constructed of any material suited for thisservice, the handle illustrated being substantially cylindrical andconcentric with the heater 1 and tip 9, but other types of handle may beused. Likewise, other means may be used of making the electricalconnections from the source of power to the heater I.

Modifications may be made within the spirit and scope of my invention,and such modifications are intended to be covered by the appendedclaims.

I claim:

1. In a soldering iron, a heater comprising a body formed of metal ofhigh thermal conductivity and enclosing an electrical heating element,terminal pins mounted at the tip end of said heater and connected incircuit with the heating element, a soldering tip secured to one end ofsaid heater and having a hollow portion and a working tip ofconsiderable mass, a thermally operated switch mounted on said terminalpins and extending into the hollow portion of said soldering tip andadjacent the working tip portion, said switch being responsive directlyto Variations in tip temperature and operatively connected to saidheating element to maintain the tip temperature substantially constant,a handle connected to the heater remotely from the tip, and means formaking electrical connections to said heating element from a source ofcurrent. 2. In a soldering iron, a heater comprising a cylindrical bodyformed of metal of high thermal conductivity and inclosing an electricalheating element, the body having reduced end portions, a handle mountedon one of said end portions and extending co -axially with the body, asoldering tip mounted on the opposite end portion and extendingco-axially with the body, a chamber in the tip between the body and thepoint of application to the work, and a thermally responsive switchmounted in said chamber and connected in circuit with said heatingelement.

iii

3. In a soldering iron, a heater comprising a solid body formed of metalof high thermal conductivity cast about an electrical heating element,terminal pins mounted at each end of said heater and connected incircuit with the heating element, means connecting the terminal pins atone end to a source of power, a thermally responsive switch mounted uponthe terminal pins at the opposite end of the heater and controlling thecircuit through said element, a soldering tip enclosing said switch, anda handle connected to the heater remotely from said tip.

4. In a soldering iron, an electrically heated body, a handle connectedthereto, a soldering tip mounted on the body, the tip having a solidworking tip portion and a chamber adjacent the same, and an adjustablethermally responsive switch mounted in the tip chamber so as to operatein accordance with variations in the working tip temperature, the switchbeing connected in circuit with the electrical heating means.

5. In a soldering iron, an electrically heated solid body, a working tipremovably mounted thereon, the tip having a hollow chamber between thebody and the point of application to the work, a. thermally responsiveswitch mounted on one end of the heater body and enclosed in thechamber, the switch being connected in circuit to control the operationof the electrically heated body to maintain the temperature of the tipsubstantially constant, and a handle detachably mounted on said body.

JOHN ERNEST SMITH.

